Java – Using a XML File (log4j2.xml) to configure Log4j 2

eclipsejavalog4j

I want to use the new Log4J 2 – Java Logging Framework. Everything work fine, but I tried since a hour to load a custom configuration file to configure the logging (like log level).

This is my log4j2.xml:

<?xml version="1.0" encoding="UTF-8"?>
<configuration status="OFF">
  <appenders>
    <Console name="Console" target="SYSTEM_OUT">
      <PatternLayout pattern="%d{HH:mm:ss} [%t] %-5level %logger{36} - %msg%n"/>
    </Console>
  </appenders>
  <loggers>
    <root level="error">
      <appender-ref ref="Console"/>
    </root>
  </loggers>
</configuration>

I tried the following, but nothing works:

Move the log4j2.xml file so it's located in the default package.
Move the log4j2.xml file anywhere in the project
Name the log4j2.xml file as "log4j.xml"
Create a folder in your project, place your log4j2.xml file there and add that folder to your runtime classpath

Since the official website can't help me, I hope you can help me get Log4j 2 working with my configuration file.

Best Answer

Important: make sure the name of the configuration file is log4j2.xml (note the 2 before the period) as opposed to log4j.xml

My guess is nothing's happening because nothing is logged using the error level. You may want to try adding another logger like so:

<logger name="com.foo.Bar" level="trace">
  <appender-ref ref="Console"/>
</logger>

Looks like the Configuration section might be a good resource.

To elaborate further, you're specifying a logger with the level set to "error":

<root level="error">
  <appender-ref ref="Console"/>
</root>

This means that only the messages logged using Level.ERROR will show up in the log. Adding a logger with a less restrictive level will allow for more messages to appear in the log. I recommend taking a look at the Architecture section of the manual (if you scroll down the page you'll see the table that explains logging levels). Alternatively, you could just change the level of the root logger to trace (instead of adding a new logger)

Given the configuration you specified, executing the code below yields something like 13:27:50.244 [main] ERROR com.example.Log4j2Tester - testing ERROR level

package com.example;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class Log4j2Tester {
    private static final Logger LOG = LogManager.getLogger(Log4j2Tester.class);

    public static void main(String[] args) {
        LOG.error("testing ERROR level");

//if you change the level of root logger to 'trace'
//then you'll also see something like
//    13:27:50.244 [main] TRACE com.example.Log4j2Tester - exiting application
        LOG.trace("exiting application");
    }
}

Related Solutions

Java – Log4j: Why is the root logger collecting all log types regardless the configuration

The root logger resides at the top of the logger hierarchy. It is exceptional in three ways:

it always exists,
its level cannot be set to null
it cannot be retrieved by name.

The rootLogger is the father of all appenders. Each enabled logging request for a given logger will be forwarded to all the appenders in that logger as well as the appenders higher in the hierarchy (including rootLogger)

For example, if the console appender is added to the root logger, then all enabled logging requests will at least print on the console. If in addition a file appender is added to a logger, say L, then enabled logging requests for L and L's children will print on a file and on the console. It is possible to override this default behavior so that appender accumulation is no longer additive by setting the additivity flag to false.

From the log4j manual

To sum up:

If you want not to propagate a logging event to the parents loggers (say rootLogger) then add the additivity flag to false in those loggers. In your case:

<logger name="org.springframework.ws.server.endpoint.interceptor"
        additivity="false">
        <level value="DEBUG" />
        <appender-ref ref="payloadAppender" />
</logger>

In standard log4j config style (which I prefer to XML):

log4j.logger.org.springframework.ws.server.endpoint.interceptor = INFO, payloadAppender
log4j.additivity.org.springframework.ws.server.endpoint.interceptor = false

Hope this helps.

Java – Configuring Log4j Loggers Programmatically

You can add/remove Appender programmatically to Log4j:

  ConsoleAppender console = new ConsoleAppender(); //create appender
  //configure the appender
  String PATTERN = "%d [%p|%c|%C{1}] %m%n";
  console.setLayout(new PatternLayout(PATTERN)); 
  console.setThreshold(Level.FATAL);
  console.activateOptions();
  //add appender to any Logger (here is root)
  Logger.getRootLogger().addAppender(console);

  FileAppender fa = new FileAppender();
  fa.setName("FileLogger");
  fa.setFile("mylog.log");
  fa.setLayout(new PatternLayout("%d %-5p [%c{1}] %m%n"));
  fa.setThreshold(Level.DEBUG);
  fa.setAppend(true);
  fa.activateOptions();

  //add appender to any Logger (here is root)
  Logger.getRootLogger().addAppender(fa);
  //repeat with all other desired appenders

I'd suggest you put it into an init() somewhere, where you are sure, that this will be executed before anything else. You can then remove all existing appenders on the root logger with

 Logger.getRootLogger().getLoggerRepository().resetConfiguration();

and start with adding your own. You need log4j in the classpath of course for this to work.

Remark:
You can take any Logger.getLogger(...) you like to add appenders. I just took the root logger because it is at the bottom of all things and will handle everything that is passed through other appenders in other categories (unless configured otherwise by setting the additivity flag).

If you need to know how logging works and how is decided where logs are written read this manual for more infos about that.
In Short:

  Logger fizz = LoggerFactory.getLogger("com.fizz")

will give you a logger for the category "com.fizz".
For the above example this means that everything logged with it will be referred to the console and file appender on the root logger.
If you add an appender to Logger.getLogger("com.fizz").addAppender(newAppender) then logging from fizz will be handled by alle the appenders from the root logger and the newAppender.
You don't create Loggers with the configuration, you just provide handlers for all possible categories in your system.

Best Answer

Related Solutions

Java – Log4j: Why is the root logger collecting all log types regardless the configuration

Java – Configuring Log4j Loggers Programmatically

Related Topic